CRYSTALLINE-STATE RACEMIZATION OF A CHIRAL CYANOETHYL GROUP CONNECTEDBY A HYDROGEN-BOND

The crystal of l]bis(dimethylgly-oximato)(pyrrolidine)cobalt(III) (dim ethylglyoximato = 2,3-butanedione dioximato) revealed a gradual change of cell parameters keeping the single-crystal form when it was irradi ated by X-rays. It contains one water molecule as solvent in the asymm etric unit. The reactive cyanoethyl group is hydrogen bonded to the wa ter molecule. In spite of the restriction by the hydrogen bond, the or dered chiral cyanoethyl group is converted to disordered racemates wit hout degradation of crystallinity. The rate of the racemization can be explained well by the cavity size of the cyanoethyl group.